Sustained-release voriconazole-thermogel for subconjunctival injection in horses: ocular toxicity and in-vivo studies.

BACKGROUND: Keratomycosis is a relatively common, sight threatening condition in horses, where treatment is often prolonged and costly. Subconjunctival (SCo) injections offer less resistance to drug diffusion than the topical route, resulting in better penetration to the ocular anterior segment. Voriconazole, a second generation triazole antifungal, is effective against common fungal organisms causing keratomycosis. If combined with a thermogel biomaterial, voriconazole can be easily injected in the SCo space to provide sustained drug release. The purpose of this study was to evaluate the drug concentrations in the anterior segment and clinical effects after SCo injections of voriconazole-containing thermogel: poly (DL-lactide-co-glycolide-b-ethylene glycol-b-DL-lactide-co-glycolide) (PLGA-PEG-PLGA) in healthy equine eyes. RESULTS: Voriconazole aqueous humor (AH) and tear concentrations were compared between 6 horses, receiving 1% voriconazole applied topically (0.2 mL, q4h) (Vori-Top) or 1.7% voriconazole-thermogel (0.3 mL) injected SCo (Vori-Gel). For the Vori-Gel group, voriconazole concentrations were measured in AH and tears at day 2 and then weekly for 23 days, and at day 2 only for the Vori-Top group. Ocular inflammation was assessed weekly (Vori-Gel) using the modified Hackett-McDonald scoring system. Ocular tissue concentrations of voriconazole following SCo 1.7% voriconazole-thermogel (0.3 mL) injections were evaluated post euthanasia in 6 additional horses at 3 different time points. Three horses received bilateral injections at 2 h (n = 3, right eye (OD)) and 48 h (n = 3, left eye (OS)) prior to euthanasia, and 3 horses were injected unilaterally (OS), 7 days prior to euthanasia. Voriconazole-thermogel was easily injected and well tolerated in all cases, with no major adverse effects. On day 2, drug concentrations in tears were higher in the Vori-Top, but not statistically different from Vori-Gel groups. For the Vori-Gel group, voriconazole was non-quantifiable in the AH at any time point. Total voriconazole concentrations in the cornea were above 0.5 µg/g (the target minimum inhibitory concentration (MIC) for Aspergillus sp.) for up to 48 h; however, concentrations were below this MIC at 7 days post treatment. CONCLUSIONS: Voriconazole-thermogel was easily and safely administered to horses, and provided 48 h of sustained release of voriconazole into the cornea. This drug delivery system warrants further clinical evaluation.

Improved Ocular Delivery of Nepafenac by Cyclodextrin Complexation.

Nepafenac is a nonsteroidal anti-inflammatory drug (NSAID), currently only available as 0.1% ophthalmic suspension (Nevanac®). This study utilized hydroxypropyl-ß-cyclodextrin (HPBCD) to increase the water solubility and trans-corneal permeation of nepafenac. The nepafenac-HPBCD complexation in the liquid and solid states were confirmed by phase solubility, differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance spectroscopy (NMR) analyses. Nepafenac 0.1% ophthalmic solution was formulated using HPBCD (same pH and osmolality as that of Nevanac®) and pig eye trans-corneal permeation was studied versus Nevanac®. Furthermore, nepafenac content in cornea, sclera, iris, lens, aqueous humor, choroid, ciliary body, retina, and vitreous humor was studied in a continuous isolated pig eye perfusion model in comparison to the suspension and Nevanac®. Permeation studies using porcine corneas revealed that the solution formulation had a permeation rate 18 times higher than Nevanac®. Furthermore, the solution had 11 times higher corneal retention than Nevanac®. Drug distribution studies using porcine eyes revealed that the solution formulation enables detectable levels in various ocular tissues while the drug was undetectable by Nevanac®. The ocular solution formulation had a significantly higher drug concentration in the cornea compared to the suspension or Nevanac®.

Comparison of the use of a standard cytology brush versus a mini cytology brush to obtain conjunctival samples for cytologic examination in healthy dogs.

OBJECTIVE: To compare the quality of conjunctival samples for cytologic examination obtained with 2 conjunctival exfoliative brushes, a mini cytology brush (MCB) and a standard cytology brush (SCB), in healthy dogs. ANIMALS: 20 client-owned dogs that were free of ocular disease. PROCEDURES: A prospective single-center randomized trial was performed. For each dog, conjunctival samples of the right eye were obtained with the 2 brushes (ie, SCB or MCB) at 2 time points that were 5 to 11 days apart. The left eye was used as a control. Cytologic quality of conjunctival samples was scored on the basis of cellularity, clearness of background, uniformity of distribution of cells on the cytology slide, artifacts, cellular overlapping, cell preservation, presence of mucus on the cytology slide, and number of RBCs. RESULTS: On cytologic evaluation, conjunctival samples collected with an SCB scored significantly better in terms of higher cellularity, less background debris, and more uniformity in the distribution of cells, compared with conjunctival samples collected with an MCB. Conjunctival samples collected with an MCB scored significantly better in terms of less cellular overlapping and less mucus in the background, compared with conjunctival samples collected with an SCB. CONCLUSIONS AND CLINICAL RELEVANCE: Overall conjunctival samples obtained with an SCB for cytologic evaluation had better diagnostic quality, compared with conjunctival samples obtained with an MCB. Use of an MCB, however, was advantageous to access localized conjunctival areas as well as collect conjunctival samples from patients with small palpebral fissures.

In Situ Gel Formulation for Enhanced Ocular Delivery of Nepafenac.

Nepafenac is a water-insoluble nonsteroidal antiinflammatory drug that is available as an ophthalmic suspension (Nevanac®). Suspensions are undesirable for 2 reasons: they tend to cause foreign body sensation and lacrimation, which could limit residence time and drug bioavailability. This decreases the amount of time the drug has to reach the site of action, the cornea. Previously, we improved the solubility and ocular permeability of nepafenac by complexing the drug with hydroxypropyl-ß-cyclodextrin. In this study, we used the complex to formulate an ion-activated in situ gel system using sodium alginate, Protanal PH 1033, to increase the residence time and to reduce repeat eye drop instillation. Rheological properties of the formulations revealed that the viscosity of the optimized formulation was increased 30-fold when exposed to the simulated tear fluid (35°C). Permeation studies showed that the drug concentration of the in situ formulations were approximately 10 times higher than the commercial product, Nevanac® (p < 0.001). In addition, the in situ gel formulations had 5-fold higher concentrations of nepafenac retained in the cornea when compared to Nevanac® (p <0.001). Finally, ex vivo drug distribution studies in the porcine eye perfusion model revealed a higher drug retention in various ocular tissues such as cornea, sclera, retina, as compared to Nevanac®.

Development of a Sustained-Release Voriconazole-Containing Thermogel for Subconjunctival Injection in Horses.

Purpose: To determine in vitro release profiles, transcorneal permeation, and ocular injection characteristics of a voriconazole-containing thermogel suitable for injection into the subconjunctival space (SCS). Methods: In vitro release rate of voriconazole (0.3% and 1.5%) from poly (DL-lactide-co-glycolide-b-ethylene glycol-b-DL-lactide-co-glycolide) (PLGA-PEG-PLGA) thermogel was determined for 28 days. A Franz cell diffusion chamber was used to evaluate equine transcorneal and transscleral permeation of voriconazole (1.5% topical solution, 0.3% and 1.5% voriconazole-thermogel) for 24 hours. Antifungal activity of voriconazole released from the 1.5% voriconazole-thermogel was determined via the agar disk diffusion method. Ex vivo equine eyes were injected with liquid voriconazole-thermogel (4°C). Distension of the SCS was assessed ultrasonographically and macroscopically. SCS voriconazole-thermogel injections were performed in a horse 1 week and 2 hours before euthanasia and histopathologic analysis of ocular tissues performed. Results: Voriconazole was released from the PLGA-PEG-PLGA thermogel for more than 21 days in all groups. Release followed first-order kinetics. Voriconazole diffused through the cornea and sclera in all groups. Permeation was greater through the sclerae than corneas. Voriconazole released from the 1.5% voriconazole-thermogel showed antifungal activity in vitro. Voriconazole-thermogel was easily able to be injected into the dorsal SCS where it formed a discrete gel deposit. Voriconazole-thermogel was easily injected in vivo and did not induce any adverse reactions. Conclusions: Voriconazole-containing thermogels have potential application in treatment of keratomycosis. Further research is required to evaluate their performance in vivo.

Effect of choroidal perfusion on ocular tissue distribution after intravitreal or suprachoroidal injection in an arterially perfused ex vivo pig eye model.

PURPOSE: To compare tissue distribution of dye-drug surrogates after intravitreal (IVT) and suprachoroidal (SCS) delivery to determine the influence of drug lipophilicity and choroidal circulation. METHODS: Thirty-two pig eyes were collected immediately after euthanasia. Sixteen eyes were perfused for 30 min through one long posterior ciliary artery with nondye containing nutrient media. An IVT or SCS injection was performed with either a 100 µL balanced salt solution (BSS, n=8), 1% sodium fluorescein (NaF, n=12) or 0.12% lipophilic carbocyanine dye (DiI, n=12). Globes were maintained at 37°C for 15 min, and then snap-frozen and dissected. Aqueous extraction and measurement of NaF or DiI concentration was performed using spectrophotometry and spectrofluorometry, respectively. RESULTS: After SCS delivery of NaF scleral, iris-ciliary body, choroidal and vitreous dye levels were higher in nonperfused eyes compared to perfused eyes. After DiI SCS or IVT delivery, no significant differences were found in dye tissue concentrations in perfused eyes compared to nonperfused eyes. Following perfusion, a better and even drug distribution was found in the retinal pigmented epithelium (RPE)-choroid following IVT and SCS delivery of the hydrophilic drug and after IVT injection of the lipophilic drug compared to nonperfused eyes. CONCLUSIONS: Choroidal circulation reduces the tissue drug concentration of the hydrophilic drug suggesting an early clearance mechanism after SCS delivery. SCS injections of lipid and hydrophilic drugs allowed direct drug delivery to the retina and RPE-choroid with limited exposition to the anterior segment.

Treatment of acute posterior uveitis in a porcine model by injection of triamcinolone acetonide into the suprachoroidal space using microneedles.

PURPOSE: To evaluate the effect of triamcinolone acetonide (TA) administered into the suprachoroidal space (SCS) using a microneedle and compare it with intravitreal (IVT) TA injections in a porcine model of acute posterior segment inflammation. MATERIALS: An IVT injection of balanced salt solution (BSS) or lipopolysaccharide (LPS) was followed 24 hours later with an injection of 0.2 mg or 2.0 mg of TA into the SCS or IVT. The SCS was accessed using microneedles in a minimally invasive procedure. Ocular inflammatory scores and IOP measurements were collected daily, whereas electroretinography, optical coherence tomography, and wide-field ocular fundus photography was performed on -1, 0, and 3 days after treatment. Aqueous and vitreous humor cell counts and protein levels and histopathology were also compared. RESULTS: Delivery of TA to the SCS using microneedles was simple, effective, and not associated with adverse effects or toxicity. SCS injection of low (0.2 mg) and high doses (2.0 mg) of TA was as effective in reducing acute inflammation in the ocular posterior segment as high-dose IVT injection. Low-dose SCS TA was also effective in reducing inflammation; however, low-dose IVT TA was not. CONCLUSIONS: Results from this study suggest that 0.2 mg and 2.0 mg of SCS TA was as effective in reducing inflammation as 2.0 mg IVT TA injection in a model of acute posterior segment inflammation. There were no adverse effects, increased IOP, or evidence of procedural or drug toxicity following injection of TA into the SCS in porcine eyes.